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From: John Baldwin <jhb@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
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Subject: PERFORCE change 93724 for review
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http://perforce.freebsd.org/chv.cgi?CH=93724

Change 93724 by jhb@jhb_slimer on 2006/03/21 18:49:19

	Use VFS locking for Giant in coredump().  Actually avoids a Giant
	leak for coredumps to a non-MPSAFE filesystem.

Affected files ...

.. //depot/projects/smpng/sys/kern/kern_sig.c#121 edit

Differences ...

==== //depot/projects/smpng/sys/kern/kern_sig.c#121 (text+ko) ====

@@ -3065,6 +3065,7 @@
 	struct mount *mp;
 	char *name;			/* name of corefile */
 	off_t limit;
+	int vfslocked;
 
 	PROC_LOCK_ASSERT(p, MA_OWNED);
 	MPASS((p->p_flag & P_HADTHREADS) == 0 || p->p_singlethread == td);
@@ -3088,21 +3089,17 @@
 	if (limit == 0)
 		return (EFBIG);
 
-	mtx_lock(&Giant);
 restart:
 	name = expand_name(p->p_comm, td->td_ucred->cr_uid, p->p_pid);
-	if (name == NULL) {
-		mtx_unlock(&Giant);
+	if (name == NULL)
 		return (EINVAL);
-	}
-	NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, td); /* XXXKSE */
+	NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, name, td);
 	flags = O_CREAT | FWRITE | O_NOFOLLOW;
 	error = vn_open(&nd, &flags, S_IRUSR | S_IWUSR, -1);
 	free(name, M_TEMP);
-	if (error) {
-		mtx_unlock(&Giant);		
+	if (error)
 		return (error);
-	}
+	vfslocked = NDHASGIANT(&nd);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	vp = nd.ni_vp;
 
@@ -3111,7 +3108,7 @@
 	    VOP_GETATTR(vp, &vattr, cred, td) || vattr.va_nlink != 1) {
 		VOP_UNLOCK(vp, 0, td);
 		error = EFAULT;
-		goto out;
+		goto close;
 	}
 
 	VOP_UNLOCK(vp, 0, td);
@@ -3126,9 +3123,10 @@
 		if (locked)
 			VOP_ADVLOCK(vp, (caddr_t)p, F_UNLCK, &lf, F_FLOCK);
 		if ((error = vn_close(vp, FWRITE, cred, td)) != 0)
-			return (error);
+			goto out;
 		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
-			return (error);
+			goto out;
+		VFS_UNLOCK_GIANT(vfslocked);
 		goto restart;
 	}
 
@@ -3153,11 +3151,12 @@
 		VOP_ADVLOCK(vp, (caddr_t)p, F_UNLCK, &lf, F_FLOCK);
 	}
 	vn_finished_write(mp);
-out:
+close:
 	error1 = vn_close(vp, FWRITE, cred, td);
-	mtx_unlock(&Giant);
 	if (error == 0)
 		error = error1;
+out:
+	VFS_UNLOCK_GIANT(vfslocked);
 	return (error);
 }